XPost: linux.debian.bugs.dist 
 From: ben@decadent.org.uk 
  
 Control: tag -1 moreinfo 
  
 On Wed, 13 Aug 2025 20:11:36 -0700 Josh Triplett  
 wrote: 
 > Package: linux-sysctl-defaults 
 > Version: 4.14 
 > Severity: wishlist 
 > File: /usr/lib/sysctl.d/50-default.conf 
 > X-Debbugs-Cc: josh@joshtriplett.org 
 > 
 > Current uses of QUIC benefit from higher buffer size limits. Please 
 > consider setting: 
 > 
 > net.core.rmem_max = 7500000 
  
 I can see that it makes sense to increase this to allow increasing the 
 receive window if the QUIC implementation sets its receive window based 
 on this, or otherwise to reduce the risk of packets being dropped if 
 user-space is slow to handle them. 
  
 I would like to see a detailed justification for the specific value, 
 though. 
  
 > net.core.wmem_max = 7500000 
  
 This seems wrong.  With QUIC the memory for replaying lost packets is 
 allocated in user-space, so I don't see any need to increase buffering 
 on the send side.  I think that this would mostly contribute to 
 bufferbloat. 
  
 > See https://github.com/quic-go/quic-go/wiki/UDP-Buffer-Sizes 
  
 No justification is given there for increasing wmem_max. 
  
 Ben. 
  
 -- 
 Ben Hutchings 
 Time is nature's way of making sure that 
 everything doesn't happen at once. 
  
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